The present invention relates generally to shunt regulators and deals more particularly with a high speed shunt regulator for supplying a load at a precise voltage level, despite high frequency fluctuations in load current.
A prior art, shunt type of voltage regulator operates from a DC source of higher voltage than the rated output voltage. The shunt regulator generates a DC current from the DC source, and the DC current flows to the load. The shunt regulator also comprises a voltage reference/current shunt circuit connected to the current source and load to shunt current not required by the load and establish a specified load voltage. For applications requiring a low shunt current, the voltage reference/current shunt circuit comprises a zener diode in parallel with the load to shunt current not required by the load and establish the load voltage. For other applications requiring a higher shunt current, the voltage reference/current shunt circuit comprises a zener diode and a pnp transistor whose base is connected to the zener diode to establish the reference voltage and whose emitter to collector path shunts the excess current to ground.
The advantage of a shunt regulator is the precision of the output voltage and ability to accommodate high frequency fluctuations in load current while maintaining rated voltage. The disadvantage is the loss of power in the zener diode and/or shunt transistor (which is not delivered to the load). The foregoing shunt regulators cannot handle very high frequency fluctuations in load current because of capacitances inherent in the current source, zener diode and transistor.
Accordingly, a general object of the present invention is to provide a shunt regulator which can handle higher frequency fluctuations in load current than the prior art shunt regulators.